Sram red crankset GXP vs BB30

Discuss light weight issues concerning road bikes & parts.
Kumppa
Posts: 202
Joined: Mon Oct 13, 2014 10:05 am

by Kumppa

Couple month ago Quarq told me this when I asked weight difference on dzrero:

Thank you for contacting me. There is roughly a 25g difference from our GXP to our BB30 cranks. The GXP is lighter for our cranks.

by Weenie


alcatraz
Posts: 1337
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

There is a pretty big difference between 68mm and 86mm spindles.

I'd be careful assuming a bb30 branded crank with a longer spindle to fit all the way through. It's a gamble. Better measure yourself to be sure.

Turning to the manufacturer might prove useless too. They might want to rebrand that crank as bb386 at a higher price, and keep the compatibility info a secret. :lol:

/a

jlok
Posts: 729
Joined: Tue Jun 30, 2015 3:30 am

by jlok

you are probably right but Quarq has the manual for bb386 installation.

https://quarq.zendesk.com/hc/en-us/arti ... _site=true
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JScycle
Posts: 232
Joined: Wed Mar 08, 2017 11:41 pm

by JScycle

Thanks everyone for your advice so far. If GXP has better bearing durability im leaning towards that.

The bike is a 2016 Scott Addict running Shimano Ultegra

hambini
Posts: 365
Joined: Tue Nov 15, 2016 8:13 am

by hambini

Here's my opinion

GXP is not the best, having a single loaded bearing on the non drive side for axial direction both ways doesn't lead to great bearing life.

BB30 in it's shorter axle length has very compact bearing spacing so the loads on it are high.

Best solution in my opinion is a BB30 with an extended length axle, some people call these BB386 but in reality they are units with a 92mm length.

Hope that helps

Hambini

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IrrelevantD
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by IrrelevantD

JScycle wrote: ↑
Wed May 09, 2018 9:48 am
Thanks everyone for your advice so far. If GXP has better bearing durability im leaning towards that.

The bike is a 2016 Scott Addict running Shimano Ultegra
From what it looks like online, the 2016 Addict is going to have PF86. Others have mentioned that the BB30 listed are actually BB386, which should work, but personally I'd go GXP.
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Rick
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by Rick

hambini wrote: ↑
Wed May 09, 2018 11:27 am
Best solution in my opinion is a BB30 with an extended length axle
How does the extended axle length make things better ?

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Calnago
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by Calnago

Extended axle in a BB30 would simply add more leverage on narrower stance bearings, creating more/faster wear and greater potential for creaking. Not ideal. Better to match the axle load from the cranks as close to the bearings as possible.
Actually, maybe that’s what Hambini was implying in his post when mentioning 386, but I can see how it could be interpreted as putting a longer 30mm spindle into a 68mm shell (hence the narrow bearing stance, long axle scenario), which would not be so great.
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hambini
Posts: 365
Joined: Tue Nov 15, 2016 8:13 am

by hambini

Calnago wrote: ↑
Thu May 10, 2018 5:03 pm
Extended axle in a BB30 would simply add more leverage on narrower stance bearings, creating more/faster wear and greater potential for creaking. Not ideal. Better to match the axle load from the cranks as close to the bearings as possible.
Actually, maybe that’s what Hambini was implying in his post when mentioning 386, but I can see how it could be interpreted as putting a longer 30mm spindle into a 68mm shell (hence the narrow bearing stance, long axle scenario), which would not be so great.
Assuming your pedal position is the same, the overall torque or leverage generated by having an extended axle or a narrow axle with more splay on the crank arms is the same.

What I was trying to say is having the bearings further apart which is more feasible on a "long" 92mm axle using 30mm bearings allows the bearing load to be reduced because the length of the cantilever is reduced.

Hambini

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